A cellular mobile communication system has a parameter referred to as “frequency reuse factor (“RF”).” In case where this reuse factor (“RF”) is 1, the same frequency is used in all sectors. In such a case, a user (i.e. terminal apparatus) at a cell edge in the boarder between neighboring cells receives interference from a neighboring cell. As a result, SINR (Signal-to-Interference and Noise Ratio) deteriorates, thereby decreasing the throughput.
By contrast with this, in case where, for example, the reuse factor (“RF”)=1/3, three frequencies are used to perform frequency allocation between cells or between sectors such that the same frequency is not used between neighboring cells or between sectors. In this case, although SINR improves, frequency use efficiency decreases by contrast because the operating band is divided into a plurality of partial bands and is used in each cell or in each sector, and therefore the frequency band used in each cell or in each sector narrows.
That is, when the reuse factor (“RF”) becomes closer to 1, the same frequency is repeatedly used between cells or between sectors, and therefore, while the frequency use efficiency improves, interference increases depending on a situation.
Hence, to secure service areas for users at cell edges and secure system throughput, the method referred to as “fractional frequency reuse” (“FFR”) has been introduced. Further, FFR includes static FFR for performing fixed frequency allocation and adaptive FFR for performing dynamic frequency allocation. For example, Non-Patent Document 1 discloses an overview of FFR.
As in the above-described case of RF=1/3, static FFR is directed to performing frequency allocation between cells or between sectors in a fixed manner. Further, Non-Patent Document 2 relates to adaptive FFR. An overview of adaptive FFR will be explained using FIG. 1. As shown in FIG. 1, according to adaptive FFR, the communication operating band is divided into a high power transmission band and a low power transmission band, and transmission power in the low power transmission band is varied stepwise to finely control gain with respect to coverage. In case where interference is reported, mode 1 transitions to mode 2 to provide a low power transmission band. In case where interference is reported even in mode 2, mode transitions to mode 3 and mode 4 to decrease transmission power in a low power transmission band. By this means, it is possible to not only provide an advantage of reducing interference upon users at cell edges and secure coverage while suppressing the decrease in throughput because the reuse factor is made 1 in the entire band except at cell edges.    Non-Patent Document 1: “Wireless broadband textbook (high speed IP wireless version),” page 266 to 268    Non-Patent Document 2: “3 GPP TSG-RAN WG1 R1-071449 (Nortel),” 3GPP LTE written contribution    Non-Patent Document 3: “3GPP TSG-RAN WG1 R1-072130 (Motorola),” 3GPP LTE written contribution.